The European Union flag is seen among EU member countries’ national flags in front of the European Parliament in Strasbourg, France.

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Citizens across the European Union will elect a new European Parliament between Thursday May 22 and Sunday May 25. Countries aren’t allowed to release official results until the last polling station closes, which happens at 11 p.m. Brussels time on the 25th.

Voters in the U.K. also head to the polls on Thursday, but lead media like the British Broadcasting Corp. won’t be releasing official exit polls or results until Sunday night. Other outlets will likely have some data on the European vote as well as results on local elections taking place at the same time will be published Thursday night. In the U.K. all eyes will be on the result for the U.K. Independence Party, which wants Britain to pull out of the EU, and how much of a battering Prime Minister David Cameron’s Conservatives will receive.

On Friday, the Irish cast their ballots, but they won’t start counting until Sunday. The Czech Republic allows its citizens to vote both Friday and Saturday.

Saturday is voting day in a bunch of smaller EU countries, namely Latvia, Malta, and Slovakia.

The real action doesn’t start until Sunday. That’s when voting starts in the remaining 21 EU countries. The first provisional results on the European level won’t be released until 11 p.m. Brussels time, when voting ends in Italy (the big story here is how much support there is for new Prime Minister Matteo Renzi’s Democratic Party and the rising Five Star Movement of comedian Beppe Grillo).

But there’s plenty of reason to pay attention before then. Between 6 p.m. and 8 p.m. we’ll get first exit polls from Germany, France and Greece, some of the most interesting countries in this election.

For Germany, the big question is how many lawmakers the euroskeptic AfD gets to send to Brussels and Strasbourg this summer. Shortly after that, we will find out whether Marine Le Pen’s National Front will actually be the biggest party in France—a development that could easily become the biggest story of the night.

In Greece, exit polls for European and local elections will give a good indication of how stable the Greek government will be as it heads into new bailout and debt-reduction talks with the rest of the euro zone. Do citizens believe center-right Prime Minister Antonis Samaras’s claims that the economy has finally turned a corner and how much of the vote goes to the leftist Syriza and the ultra-right Golden Dawn?

Other countries to pay attention to are Finland, where the The Finns (the nationalist party you may remember as the True Finns) are currently head-to-head with the center-right Kokoomus (part of the European People’s Party) and Denmark, where the nationalist Danish People’s Party has been making gains.

At 9 p.m. the Parliament publishes figures on turnout—an closely-watched metric after only 43% of potential voters cast their ballots in 2009—and at 10 p.m. the chamber will release a first estimate of its future make-up (just in time for print deadlines across the continent).

Of course, many of the key questions won’t be answered until some time after May 25. For instance, will far-right parties really manage to form an official voting group (which gives lawmakers extra funding and the right to lead negotiations on new laws) and will the European Conservatives & Reformists (home to the U.K. Conservatives) maintain enough delegates to do the same?

And of course, perhaps the biggest question: Will EU leaders actually appoint the lead candidate of the winning party (i.e. the Socialists’ Martin Schulz or the EPP’s Jean-Claude Juncker) as commission president? We may get a first indication the night of Tuesday May 27, when national prime ministers and presidents meet in Brussels for an informal dinner, but don’t count on all mysteries being resolved by then.

Before all this, keep an eye on our election infographic, which will be updated with the latest polls until the day before voting starts.

Corrections & Amplifications: An earlier version of this article said exit polls on European election in the U.K. will be published Thursday night, but lead media like the BBC won’t be publishing opinion polls on the European vote until Sunday night.

About Real Time Brussels

The Wall Street Journal’s Brussels blog is produced by the Brussels bureau of The Wall Street Journal and Dow Jones Newswires. The bureau has been headed since 2009 by Stephen Fidler, who was previously a correspondent and editor for the Financial Times and Reuters. Also posting regularly: Matthew Dalton, Viktoria Dendrinou, Tom Fairless, Naftali Bendavid, Laurence Norman, Gabriele Steinhauser and Valentina Pop.